Hosts file ignored; OWA publishing on ISA 2004, Windows Server 2003

Posted on 2008-11-20
Last Modified: 2012-05-05

I'm trying to publish an Exchange 2000 server behind an ISA server 2004 using SSL.
I have configured everything including the certificates as per this article:

However I am unable to get the hosts file entry on the ISA server to work correctly. The article recommends this entry and the reason for this is:

"The ISA firewall must be able to resolve the name used by remote users connecting to the OWA site through the ISA firewall to the IP address of the OWA site on the corporate network. The ISA firewall must NOT resolve this name to the IP address on the external interface of the ISA firewall."

For some reason my hosts file is being ignored and the ISA server is resolving the OWA URL to the IP associated with the external adapter, not the internal exchange server that I have specified in the hosts file. Pinging the OWA URL from the ISA console resolves and replies from the ISA's external interface.  OWA is working correctly internally. Externally entering the OWA URL into a browser gives me a warning about a certificate from an currently untrusted source (which I would anticipate) and then when I choose to continue returns the error:

Error Code: 500 Internal Server Error. Internet Control Message Protocol (ICMP) network is unreachable. For more information about this event, see ISA Server Help

I'm not sure if this could be a factor; but the ISA's external adapter is attached to a cable modem,  and it has to obtain its IP address from the cable modem automatically. However the ip address, gateway and other information the modem hand out always remain the same.

I realise that this is an unusal setup, but this an ISP limitation with their static IP service.
Regardless, ISA has been functioning correctly using this configuration and is supporting several VPN tunnels and other publishing rules without issue.

ISA Server 2004 running on Windows 2003
Exchange 2000 Running on Windows 2000 SP4

Please can anyone help?

thanks in advance.
Question by:thinkjim
    LVL 10

    Expert Comment

    The ISA Server will check cache before checking HOSTS
    If you run ipconfig /flushdns or just reboot it should cure the issue

    Author Comment


    Yes I have already tried flushing the DNS and also rebooting, to no effect :(
    LVL 10

    Accepted Solution

    Please forgive me for asking these questions (!) but it's eliminate the obvious before getting complicated time.
    The HOSTS file is just HOSTS and not HOSTS.SAM?
    It is in the c:\<windir>\system32\drivers\etc folder?
    You have used the syntax
    <ip_addr> <tab> <hostname>
    The hostname is JUST the netbios name and not the FQDN?
    there's no # or other comment symbol in the hosts file
    Again - sorry for the obvious micky mouse stuff, but sometimes it's worth checking!
    Oh, if you type drivers in Start,run it gets you to the folder much more quickly.

    Author Comment

    Hi Kieran,

    thanks for your help. I think I was having a moment of clinical insanity. I'm a sysadmin so I should know better!

    Having rebooted the machine, cleared out the hosts file etc, it all seems to be working properly now. Thank you for your help.

    LVL 10

    Expert Comment

    We all do! :-)
    Sometimes, it's worth just posting up to clarify our own thoughts. It's actually why I sometimes reply with the "back to basics" statements.
    Glad it's sorted

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